Article

Design of a Multi-Stage Microfluidics System for High-Speed Flow Cytometry and Closed System Cell Sorting for Cytomics

Proceedings of SPIE - The International Society for Optical Engineering (Impact Factor: 0.2). 12/2008; 6859. DOI: 10.1117/12.764037

ABSTRACT To produce a large increase in total throughput, a multi-stage microfluidics system (US Patent pending) is being developed for flow cytometry and closed system cell sorting. The multi-stage system provides for sorting and re-sorting of cohorts of cells beginning with multiple cells per sorting unit in the initial stages of the microfluidic device and achieving single cell sorting at subsequent stages. This design theoretically promises increases of 2- or 3-orders of magnitude in total cell throughput needed for cytomics applications involving gene chip or proteomics analyses of sorted cell subpopulations. Briefly, silicon wafers and CAD software were used with SU-8 soft photolithography techniques and used as a mold to create Y-shaped, multi-stage microfluidic PDMS chips. PDMS microfluidic chips were fabricated and tested using fluorescent microspheres driven through the chip by a microprocessor-controlled syringe drive and excited on an inverted Nikon fluorescence microscope. Inter-particle spacings were measured and used as experimental data for queuing theory models of multi-stage system performance. A miniaturized electronics system is being developed for a small portable instrument. A variety of LED light sources, waveguides, and APD detectors are being tested to find optimal combinations for creating an LED-APD configuration at the entry points of the Y-junctions for the multi-stage optical PDMS microfluidic chips. The LEDs, APDs, and PDMS chips are being combined into an inexpensive, small portable, closed system sorter suitable for operation inside a standard biohazard hood for both sterility and closed system cell sorting as an alternative to large, expensive, and conventional droplet-based cell sorters.

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    • "were designed and manufactured using standard photolithography and soft lithography techniques in the cleanroom of the Birck Nanotechnology Center at Purdue University (Grafton, 2008). Performance of the chip was evaluated by visual observation of fluorescent microspheres and stained cells flowing through the device whilst situated upon an inverted fluorescent microscope. "
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    • "were designed and manufactured using standard photolithography and soft lithography techniques in the cleanroom of the Birck Nanotechnology Center at Purdue University (Grafton, 2008). Performance of the chip was evaluated by visual observation of fluorescent microspheres and stained cells flowing through the device whilst situated upon an inverted fluorescent microscope. "
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    ABSTRACT: Point-of-care devices represent the future for medical technologies. Current diagnostic tools are cumbersome, expensive, complicated, and often at risk for contamination. There is a need for cost effective, portable, closed-system, high-speed cell screening and cell isolating device. A microfabricated, exponentially-staging, BioMEMS microfluidic cytometer/cell sorting device offers these advantages over current technologies. A two-stage branched architecture allows the study of inter-particle spacing, flow relations, pressure measurements, and cell behavior in an environment where fluorescence detection is used to identify and analyze certain cellular characteristics. This device was microfabricated using the polymer PDMS to transmit light effectively, to be inexpensive and disposable, and to be easy to manipulate. For initial prototyping, an inverted fluorescent Nikon microscope provided the necessary excitation to view the particles and cells. For the portable device, avalanche photo diodes (APDs) and light emitting diodes (LEDs) are being incorporated into the device for the detection and excitation respectively. For low light level applications, sigma-delta modulation methods are being applied to reduce noise susceptibility and to detect the APD signal more efficiently. In addition, a data acquisition system (DAQ) has been designed that can effectively track signals from a cell sorter using a digital signal processing (DSP) board and a laptop computer. Currently elastomeric valves for diverting flow have been incorporated into the microfluidic chip. Measurements are being made of the effects of the microfluidics valve structures, or the simple opening and closing of selected channels to divert flow and cells down specific channels depending on their measured properties.
    Proceedings of SPIE - The International Society for Optical Engineering 02/2009; DOI:10.1117/12.809854 · 0.20 Impact Factor
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    ABSTRACT: The proposed sensor interface minimizes the optical detection system size while maximizing its overall efficiency (both power and sensitivity) of a multi-stage microfluidic cell sorter system. The proposed SigmaDelta sensor interface achieves at least one order of magnitude higher sensitivity while consuming less power (2mW) as compared to the traditional operational amplifier based transimpedance amplifier sensor interface. The proposed SigmaDelta sensor interface will be used to complete a full implementation of the developed multi-stage microfluidic system that would prove to be a great advancement in microfluidic cell sorting technology.
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